The architecture of Microsoft MSSQL Server is mainly divided into three components:

1. SQLOS: which implements the basic services required by MS SQL Server, including thread scheduling, I/O stat management and memory management.

2. Relational Engine: which implements the relational database components including support for databases, tables, queries and stored procedures as well as implementing the type system.

3. Protocol Layer: which exposes the MS SQL Server functionality.

SQLOS

SQLOS is the base component in the Windows SQL Server architecture. It implements functions normally associated with the Operating System, thread scheduling, memory management, I/O management, buffer pool management, resource management, synchronization primitives and locking, and deadlock detection. Because the requirements of Windows SQL Server are highly specialized, it implements its own memory and thread management system, rather than using the generic one implemented in the OS. SQLOS also includes synchronization primitives for locking as well as monitoring for the worker threads to detect and recover from deadlocks.

more…

There are several points that Microsoft suggests before configuring your MS SQL Server.

BEST PRACTICES ACCORDING TO MICROSOFT

• Install only those components that you will use immediately. Microsoft recommends that you create a list of components that you will be using, and only enable those. If the need arises, you can install the additional components at that time. The components in a SQL Server installation are the Database Engine, Analysis Services Engine, Reporting Services, Integration Services, Notification Services, and Documents and Samples.

• Enable only the optional features you will use, and review optional feature usage before doing an in-place upgrade and disable unneeded features. Microsoft recommends that you create a list of the optional features that you will use, and only turn those on. If this is an existing SQL Server that is being upgraded, they recommend creating the same list, and disabling any optional features not on the list. These optional features are CLR Integration, OLE Automation, remote use of a dedicated administrator connection, Database Mail and SQL Mail, OpenRowset and OpenDataSource functions, SQL Server Web Assistant, and xp_cmdshell availability.

more…

Enable remote connections for SQL Server 2005 Express or SQL Server 2005 Developer Edition

You must enable remote connections for each instance of SQL Server 2005 that you want to connect to from a remote computer. To do this, follow these steps:

1.    Click Start, point to Programs, point to Microsoft SQL Server 2005, point to Configuration Tools, and then click MS SQL Server Surface Area Configuration.
2.    On the MS SQL Server 2005 Surface Area Configuration page, click Surface Area Configuration for Services and Connections.
3.    On the Surface Area Configuration for Services and Connections page, expand Database Engine, click Remote Connections, click Local and remote connections, click the appropriate protocol to enable for your environment, and then click Apply.

Note Click OK when you receive the following message:
Changes to Connection Settings will not take effect until you restart the Database Engine service.
4.    On the Surface Area Configuration for Services and Connections page, expand Database Engine, click Service, click Stop, wait until the MSSQLSERVER service stops, and then click Start to restart the MSSQLSERVER service.

Enable the SQL Server Browser service

If you are running MS SQL Server 2005 by using an instance name and you are not using a specific TCP/IP port number in your connection string, you must enable the SQL Server Browser service to allow for remote connections. For example, MS SQL Server 2005 Express is installed with a default instance name of Computer Name\SQLEXPRESS. You are only required to enable the SQL Server Browser service one time, regardless of how many instances of SQL Server 2005 you are running. To enable the MS SQL Server Browser service, follow these steps.

more…

Some times we see the error below in the event logs:

“SQL Server has encountered 1 occurrence(s) of I/O requests taking longer than 15 seconds to complete on file [T:\MSSQL\DATA\%file_name%] in database [%DB_name%] (2).  The OS file handle is 0×00000838.  The offset of the latest long I/O is: 0×000000ebdc0000“

Do you refer it to as a stalled IO? We always hear a questions such as, what’s wrong with SQL Server..? Why is SQL taking so long to read or write to the disk..? Let us discuss why it is not a MS SQL Server problem:

MS SQL Server does data file reads and writes almost exclusively as asynchronous IO, using the win32 APIs ReadFile, WriteFile, ReadFileScatter and WriteFileGather. Each of these APIs behave in a fairly similar steps, the caller sends in a handle to the file, some memory location to read or write, the size of the block and a structure that tells the kernel how to handle the IO. In MS SQL Server’s case, how to handle the IO is Asynchronously, please.  The call returns immediately so that the thread issuing so that the IO can get out of the way and make life happy for other users who are also waiting got their query to return.

The catch here is that, ordinarily the time between the Asynchronous call to read or write and the completion of the read or write should be on the order of 10ms. The longer it takes for an IO to return the more noticeable a performance impact there is to end users.

more…